src/zlib/adler32.c

/* adler32.c -- compute the Adler-32 checksum of a data stream
 * Copyright (C) 1995-2002 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/* @(#) $Id$ */

#include "../zlib/zlib.h"

#define BASE 65521L /* largest prime smaller than 65536 */
#define NMAX 5552
/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */

#define DO1(buf,i)  {s1 += buf[i]; s2 += s1;}
#define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
#define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
#define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
#define DO16(buf)   DO8(buf,0); DO8(buf,8);

/* ========================================================================= */
#if defined(__VISAGECPP__) /* Visualage can't handle this antiquated interface */
uLong ZEXPORT adler32 (uLong adler, const Bytef* buf, uInt len)
#else
uLong ZEXPORT adler32(adler, buf, len)
    uLong adler;
    const Bytef *buf;
    uInt len;
#endif
{
    unsigned long s1 = adler & 0xffff;
    unsigned long s2 = (adler >> 16) & 0xffff;
    int k;

    if (buf == Z_NULL) return 1L;

    while (len > 0) {
        k = len < NMAX ? len : NMAX;
        len -= k;
        while (k >= 16) {
            DO16(buf);
	    buf += 16;
            k -= 16;
        }
        if (k != 0) do {
            s1 += *buf++;
	    s2 += s1;
        } while (--k);
        s1 %= BASE;
        s2 %= BASE;
    }
    return (s2 << 16) | s1;
}
Commit	Line	Data
	1	/* adler32.c -- compute the Adler-32 checksum of a data stream
	2	* Copyright (C) 1995-2002 Mark Adler
	3	* For conditions of distribution and use, see copyright notice in zlib.h
	4	*/
	5
	6	/* @(#) $Id$ */
	7
	8	#include "../zlib/zlib.h"
	9
	10	#define BASE 65521L /* largest prime smaller than 65536 */
	11	#define NMAX 5552
	12	/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
	13
	14	#define DO1(buf,i) {s1 += buf[i]; s2 += s1;}
	15	#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
	16	#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
	17	#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
	18	#define DO16(buf) DO8(buf,0); DO8(buf,8);
	19
	20	/* ========================================================================= */
	21	#if defined(__VISAGECPP__) /* Visualage can't handle this antiquated interface */
	22	uLong ZEXPORT adler32 (uLong adler, const Bytef* buf, uInt len)
	23	#else
	24	uLong ZEXPORT adler32(adler, buf, len)
	25	uLong adler;
	26	const Bytef *buf;
	27	uInt len;
	28	#endif
	29	{
	30	unsigned long s1 = adler & 0xffff;
	31	unsigned long s2 = (adler >> 16) & 0xffff;
	32	int k;
	33
	34	if (buf == Z_NULL) return 1L;
	35
	36	while (len > 0) {
	37	k = len < NMAX ? len : NMAX;
	38	len -= k;
	39	while (k >= 16) {
	40	DO16(buf);
	41	buf += 16;
	42	k -= 16;
	43	}
	44	if (k != 0) do {
	45	s1 += *buf++;
	46	s2 += s1;
	47	} while (--k);
	48	s1 %= BASE;
	49	s2 %= BASE;
	50	}
	51	return (s2 << 16) \| s1;
	52	}